1. Field of the Invention
The present invention relates generally to the art of mixing paddles and more specifically to the art of paddles used for mixing two or more components in a vat. Still more specifically, the preferred embodiment of the present invention relates to a mixing paddle for use in creaming of cottage cheese curd, and which permits extremely effective mixing and which does not damage the relatively delicate curd particles.
2. Description of the Prior Art
Numerous processing devices are known to the art for mixing process materials in a vat or other container. One illustrative type of process is the processing of cottage cheese, but it should be understood at the outset that the mixing paddle of the present invention has numerous other applications. These will become apparent to those skilled in the art after the present invention has been described.
Problems with prior art mixing machines, and mixing paddles in general, include the ability of the machines to adequately mix all the materials contained in the vat, e.g. the ability to pick up and dispense and mix the process materials located at the bottom, ends and corners of the vat. Furthermore, most prior art mixing machines are not entirely suitable if one of the process materials to be mixed is delicate, e.g. the curd particles of cottage cheese. Agitation of the process materials throughout the depth of the vat is also a problem resulting in a final product having varying degrees of mix consistency. Many prior art mixing paddles are of the push variety, in which cases relatively small paddles have to be used due to the large blade loads. Stirring paddles used in the past include those discussed below, as well as those described in U.S. Pat. Nos. 3,476,364 and 3,490,751 assigned to the assignee of the present invention.
The prior art known to the present inventors to which the invention is most closely related is the "Wing Iype Agitator" shown in U.S. Pat. No. Re. 30,237, reissued Mar. 25, 1980 to Born. In this device, an agitator carriage is supported above and is powered for oscillatory movement along the length of a rectangular, elongate vat. A pair of stirring blades depend below the carriage into the vat and overlap one another in the vat for more complete mixing. Each blade is supported to move through a generally circular path in a vertical plane, and the blades are rotated independently of the motor which drives the carriage along the length of the vat, resulting in each blade having both vertical and horizontal components as it moves through the vat. By varying the speed of the carriage motor and the blade motor, loops of movement are created by mixing paddles carried on the lower ends of the blades, which loops can vary from being generally circular in shape to a pattern which is more undulating. Some limited pivoting of the paddles is permitted with this device, but it still suffers from two significant drawbacks. These drawbacks are first the tendency of the paddles to push down onto (crush) the cottage cheese curds and the fact that the paddles do not entirely mix the processing materials in the vicinity of the ends and end corners of the vat, as well as scraping the bottom. The latter problem leads to the need to employ laborers to manually assist in the mixing process.
Other examples of mixing devices known prior to the present invention include the "Cheese Making Apparatus" shown in Jenks' Nov. 7, 1882 U.S. Pat. No. 267,211. In this device a cheese curd cutter includes a rod or shaft having an agitator at its lower end. The shaft can be rotated about its axis and reciprocated in a longitudinal plane.
Another "Mixing Machine" is described in U.S. Pat. No. 707,261 issued to Ruttkamp on Aug. 19, 1902. In this patent a semi-circular tank is used to contain the processing materials and a beam is supported on the top of the tank. The beam supports a windmill like blade which rotates in a vertical plane. The device discloses a mechanism for reversing the movement of the mixing rotator.
Gowan, in his U.S. Pat. No. 852,116 issued Apr. 30, 1907 for "Agitator" describes a dasher which swings and is reciprocated and which includes wing-like elements set at an angle with respect to one another. The patentee indicates that this device works cottage cheese curd vertically and longitudinally in a vat.
A "Stirring Paddle Assembly For Process Vat" is shown in Thomson's U.S. Pat. No. 3,476,364 issued Nov. 4, 1969. In this device for cheese processing, a single stirring blade is connected to and trails each arm of a paddle assembly. The blade extends substantially above the bottom of the vat so that areas above the bottom will be stirred as a central rotating hub, to which the arms are attached, is moved transversely above and along the vat.
While each of the foregoing patents identifies the need for improvement in mixing efficiency, some even for delicate process materials, they all suffer from one or more drawbacks such as those discussed at the first part of this section of the specification. A mixing assembly which includes an improved mixing paddle to overcome such drawbacks would represent a substantial advance in the art.